1. Field of the Invention
The present invention relates to an image forming apparatus, in particular, a structure of an interior member capable of controlling noise from a main body of an image forming apparatus, and to a method of designing a frame.
2. Description of the Related Art
Conventionally, it has been an important subject to prevent noise generated in an image forming apparatus from leaking outside.
FIG. 15 is an external structural view of a conventional image forming apparatus.
Referring to FIG. 15, a conventional image forming apparatus 1000 is provided with an exterior cover 45 on the front, back and lateral side faces so as to cover the entire apparatus main body for controlling the noise from the apparatus main body which is not illustrated in the drawing. In image forming apparatus 1000 shown in FIG. 15, a case in which a sheet feed tray 1030, a sheet discharge tray 16 and a display 1020 are provided as well as the exterior cover 45 is illustrated.
FIG. 16 is a diagram illustrating part of the structure of an apparatus main body of an image forming apparatus.
Referring to FIG. 16, a color printer is shown in which a color image is formed electrophotographically using a photoconductor 1 of a drum type serving as a latent image carrier, four developers configuring a developing unit 6, and an intermediate transfer belt 7a serving as an image carrier belt. In this context, description will be made only for principal parts of the image forming apparatus.
Specifically, there are provided photoconductor 1 of a drum type as one example of an image carrier, which is, for example, rotated for image formation; developing unit 6 including a plurality of, e.g., four developers, for forming toner images by development onto a moving face of photoconductor 1; and an intermediate transfer unit 7, which, for example, rotationally moves in synchronization with photoconductor 1, so that toner images sequentially formed on the moving face of photoconductor 1 are sequentially overlaid and transferred at a transfer position set around the moving face of photoconductor 1.
In photoconductor 1, an electric latent image according to an image signal, namely, an electrostatic latent image is formed for each color in response to image exposure by a laser beam 9 modulated by the image signal from a laser print head 8, or in response to optical printing, and then the latent image is visualized by development and formed into a toner image.
With regard to the development of an electric latent image, a toner image on photoconductor 1 is electrostatically transferred onto intermediate transfer belt 7a of intermediate transfer unit 7 by electrostatic absorption upon application of electric charge from a transfer roller 11 serving as a primary transfer unit.
A toner image resulting from sequential overlaying onto intermediate transfer belt 7a, electrostatic transferring, and image composition is then secondary-transferred electrostatically at once onto a transfer sheet fed from a sheet feed part 12a or the like at a transfer position set around the moving face by electrostatic absorption from a transfer roller 14 serving as a secondary transferring unit. Then the transfer sheet after the secondary transfer is passed through a fixing unit 15 to complete the image formation, and then discharged onto a sheet discharge tray 16.
Both the primary transfer and the secondary transfer may adopt transfer methods other than the electrostatic transfer, corresponding to a developing method employed in the image formation. Fixing unit 15 may also be adapted to the developing method, and it is sometimes unnecessary.
For color image formation, the plurality of developers develop an electrostatic latent image with toners 2a to 5a of respective colors, yellow, magenta, cyan and black, respectively, and in the present example, fixing unit 15 employing heating or pressuring, or both is used in association with the use of powder resin toners. Use of the developer for black is not essential.
A color image may be formed using four or more developers. The present invention is applicable to the case where two or more developers are alternately used without limited to the case where a color image is formed.
Photoconductor 1 forms a process unit 36 having a charging charger 34 and a cleaner 35.
FIG. 17 is a perspective view of an apparatus main body of an image forming apparatus.
Referring to FIG. 17, here is shown a perspective view of the apparatus main body of the image forming apparatus in which exterior cover 45 is removed. Here, the apparatus main body is provided, and a frame 1100 as an interior member securing and supporting the apparatus main body is illustrated.
Here is also shown developing unit 6 having four developers as described above.
Also shown is the case in which various motors for driving the apparatus main body are arranged with respect to frame 1100. Specifically, motors M1 to M4 for respectively driving above-mentioned developing unit 6, intermediate transfer belt 7a, transfer roller 11 and the like are arranged. Also a fan FN is arranged.
Since the rotation mechanism based on these motors M1 to M4 and the like and driving of fan FN and the like generate noises, a method of increasing transmission loss of sound by increasing surface density of the exterior member by increasing the thickness or mass of the exterior cover as an exterior member for controlling noises, or a method of bonding a sound absorbing material to the exterior member have been conventionally adopted.
Also known is a method of reducing noises by forming the exterior member of a laminate in which a solid layer and an air layer are alternately laminated, or employing a hollow double wall structure.
Further, in Japanese Laid-Open Patent Publication No. 2000-235396, a method of reducing noises by designing the exterior member to constitute a HelmHoltz resonator is disclosed.
However, in such conventional noise reduction structures, the size or weight of the apparatus may be increased, and the costs may increase from the viewpoint of material because the method is based on increasing the thickness or weight of the exterior member.
Also in the method of using a sound absorbing material, ensuring of a space for bonding the sound absorbing material, as well as the material cost of the sound absorbing material, is required.
Generally, there is correlation between the thickness of a sound absorbing material and the sound absorbing performance, so that the size of apparatus may be increased.
Further, in the exterior member as described above, employing the laminate structure or hollow double wall structure is disadvantageous in terms of cost, and may increase the size and weight of apparatus.
Also in the case where a HelmHoltz resonator is configured in the exterior member, similar problems arise. In the case of HelmHoltz resonator, there is an additional problem that the frequency of the sound to be absorbed is limited, and the design may become complicated.